3) If it is kept only four control points-at the'angles'of'the 
block it is obtained the following results, with the three 
kinds of GPS data-- 
  
  
Differential Pseudoranges and phases Pseudoranges 
Tx 0,79 m 0,77 m 1,29 m 
Ty 0,63: m 0,64 m 2,32- m 
Tz 0,51 m 0,53 m 0,98 m 
  
  
  
  
  
  
4) When"all the control points are eliminated it is kept only 
one-imaginary point without error, at the center of the block, 
with the following results : 
  
  
Differential Pseudoranges and phases Pseudoranges 
Sad DM 0,25 m 1,04 m 
Ty 0,67 m 0,70 m 1,27 m 
TZ 0,56™m 0,63 m 0,93 m 
  
  
  
  
  
  
Comparison of the previous results involves the following re- 
marks : 
l) results are not really affected by elimination of control 
points of which accuracy seems lower than those of GPS measure- 
ments. This fact can be explained by the kind of the used con- 
trol points (it is natural points) and the accuracy losses due 
to transfer of points on the 1987 photoflight. 
2) Contribution of differential measurements appears negligible 
3) Results with only pseudoranges are not so bad as it was fea- 
red, particularly with an imaginary control point. In fact it is 
the photogrammetric block itself which ensures smoothing func- 
tion. 
4) North-South strips play an important part to ensure stiff- 
ness of the block, for instance in altimetry. When these strips 
are eliminated from photogrammetric adjustment there is no im- 
portant effect in planimetry but a high degradation in altime- 
trv. 
C) Vichy test site 
  
For this sheet we have only differential and pseudoranges 
smoothed by phase GPS data. 
This sheet has a better ground equipment that the Lunel one 
because there was a ground preparation just after the aerial 
survey, in 1987." Aerial triangulation gives, therefore, better 
results, with adjustment residuals on control points as follows: